问题 选择题

4.6g某有机物完全燃烧需要9.6g氧气,生成8.8g二氧化碳和5.4g水,由此可以判断此有机物中(  )

A.只含碳、氢两种元素

B.含有碳、氢两种元素,可能含有氧元素

C.只含碳、氢、氧三种元素

D.含有碳、氢两种元素,不含氧元素

答案

由质量守恒定律可推断该有机物中一定含有碳、氢两种元素,可能含有氧元素.8.8gCO2中碳元素的质量为8.8g×

12
44
5=2.4g,5.4gH2O中氢元素的质量为5.4g×
2
18
=0.6g,

故该有机物中碳元素和氢元素的质量为2.4g+0.6g=3g,小于有机物的质量4.6g,所以该有机物中含有氧元素.

故选C.

完形填空

Are you a man or a mouse? When people ask this question they want to know     you think you are a     person or a coward (懦夫). But you will never really know the answer to this question     you are tested in real life. Some people    they are brave but when they come face to face with real    , they act like cowards. Others think of themselves as cowards, but when they meet danger, they act like heroes.

Lenny had always thought of himself as a nervous person. He got worried before examinations. He worried about his job and health. All he wanted in life was to be safe and healthy. But    December 15th, 2013, a plane crashed into a river in Washington. Lenny went to the river to see what was happening. He saw a woman in the     water. Lenny did not feel afraid. He behaved very    and did a very dangerous thing. He jumped into the river and    to the woman, and kept her head above the water. Seventy-eight people died that day. Thanks to Lenny, it was not    .

When you are in a very dangerous situation and feel afraid, the body automatically(自动地) produces a chemical in the blood. The chemical is called adrenalin(肾上腺素). With adrenalin in the blood system, you actually feel stronger and stronger and are ready to fight.

小题1:A. neither B. whether  C. either

小题2:A. brave   B. real C. hard

小题3:A. when    B. until    C. after

小题4:A. realize B. find C. think

小题5:A. question    B. mouse    C. danger

小题6:A. on  B. in   C. for

小题7:A. fresh   B. warm C. ice-cold

小题8:A. nervously   B. calmly   C. fearfully

小题9:A. went    B. spoke    C. swam

小题10:A. an accident    B. seventy-eight    C. seventy- nine

选择题